Connections between reinforced, precast concrete structures and method of making same



Aug. 16, 1960 v M. H. R. coGAN 2,948,995

CONNECTIONS EETwEEN EETNEOECEO, PEE-CAST CONCRETE STRUCTURES ANO METHODOE MAKING SAME 5 Sheets-Sheet l Filed Feb. 24. 1953 NvENToz:

MYLEs n.12. COGAN EN ws ATTORNEY.

Aug. 16, 1960 M.' H. R. coGAN 2,948,995

CONNECTIONS BETWEEN REINFORCED, PRECAST CONCRETE STRUCTURES AND METHOD0E MAKING SAME 5 Sheets-Sheet 2 Filed Feb. 24, 1953 INVENTOR- FIC-1. C:

MYLES H. E. COC-AAN f- MAM N5 ATTORNEY Aug. 16, 1960 M. H. R. coGAN2,948,995

CONNECTIONS BETWEEN REINF'ORCED, PRE-'CAST CONCRETE STRUCTURES ANDMETHOD oF MAKING SAME |NVENTOR: MYLE5 H.R..COC1AN HE ATTORNEY M. H. R.coGAN 2,948,995

PRE-CAST CONCRETE AKING SAME 5 Sheets-Shevec` 4 nvenlror Mqee HR. ClownEL; m His M'fomeq CONNECTIONS BETWEEN REINF'ORCED,

STRUCTURES AND METHOD OF' M Aug. 16, 1960 Filed Feb. 24, 1953 Aug. 16,1960 M. H. R. coGAN 2,948,995

CONNECTIONS BETWEEN REINFORCED, PRE-CAST CONCRETE STRUCTURES AND METHODOF MAKING SAME Filed Feb. 24. 195s 5 sheets-sheet 5 HG. 15. I

los i lOB 5' Mes H- dn EL) His AJH-meg CONNECTIONS BETWEEN REINFORCED,-PRE- CAST CONCRETE STRUCTURES AND METHOD F MAKING SAW Myles H. R.Cogan, Houston, Tex., assignor to Shell gli Company, New York, N .Y., acorporation of Delaare Filed Feb. 24, 1953, Ser. No. 338,293

20 Claims. (Cl. Sil- 179) This invention relates to connections betweenmetalreinforced, separately cast concrete structures, e.g., between apre-cast superstructure that has one or more metal reinforcing rods andthe support therefor, such as a foundation, column or girder havingsimilar rods, and to a method of making such connections, viz., oferecting a superstructure on a support, etc. The structures may, forexample, be parts of a building, such as walls, columns, glrders, beamsor floor slabs, or may be poles or stanchions for supporting cables,pipes, power lines or the like, columns for elevated roadways orfoundations.

Reinforced concrete structures of the type indicated above arefrequently o-f such size or shape as to make it impracticable oruneconomical to cast two or more of them integrally. Thus, it is commonto cast a supported structure separately from the support or foundationtherefor and to erect or cast the latter as a separate structure at thesite of erection and subsequently attach the pre-cast supportedstructure. This is usually accomplished by ailixing mating brackets orbed plates to the pre-cast supported structure and to the supportingstructure and connecting the brackets or plates of the two structures bybolting or the like. Such brackets or plates must be precisely leveledto the supporting structure or shims or the like must be employed toposition the supported pre-cast structure in the desired, predeterminedlocation and this necessitates some care in the installation of thesupport and/ or the making of the connection. Moreover, to develop the-desired tensile stress in the reinforcing rods of the structureentirely to the juxtaposed parts of the two structures it is necessaryto bond the rods to the brackets or bed plates, which further adds tothe cost, especially when precise positioning is required. Y

It has not heretofore been feasible to join such separately caststructures by merely welding or otherwise connecting projectingreinforcing rods between two spacedV structures and then filling the gapbetween the structures with fresh concrete or grout and permitting thelatter to set for the reason that the latter shrinks during hardening,

whereby the full strength in compression of the iilling material is notdeveloped over the full area of the juxtaposed parts of the structures.This causes non-uniform application of compressive stresses at theconnection when the latter is subjected to loading. This is particularlyobjectionable and causes high localized compressive stresses when theconnection is subjected to bending moments, eg., when a column connectedthereby is subjected to a horizontal force applied at some distanceabove the connection or when a beam having a cantilever connection isloaded. Moreover, in such a connection the metal reinforcing rods arenot always adequately loaded to the juxtaposed ends of the structures,preventing early` of the rods;

development of the full tensile strengths further, this makes itimpracticable to pre-stress the rods at the connection, suchpre-stressing being desirable in` certain installations.

Itis an object of this invention to provide an improved Patented Aug.16, 1960 ice connection between separately cast metal-reinforcedstructures and an improved method of making the same wherein the metalreinforcing rods are connected to develop tensile stress across theconnection for anchoring the two parts together, and wherein the fullcompressive strength of the lling material is developed over the crosssectional area of the juxtaposed parts of the structures which does notrequire the use of bed plates, brackets, or the like. Ancillary thereto,it is an object to provide an improved connection and method of the typeindicated wherein the reinforcing rods may, if desired, be prestressedat the connection.

A specific object is to connect a pre-cast, metal-reinforced concretestructure such as a column or the like on a support, such as afoundation, to achieve a secure anchoring of the structure to thesupport against tilting and afford substantially uniform `distributionof compressive stresses over the cross sectional area of the connectionwithout the use of bed plates or the like.

A further object is to provide an improved connection and method oferection of the type described that is more economical and is simplyapplied in practice to a variety of pre-cast structures.

Still another object is to provide a connection and method of erectionwhereby the exact location of the pre-cast structure in relation to thesupport can be adjusted, within limits, to fit the former into thedesired conformation to other elements of a composite structure, such asa row of similar structures, a house having several pre-cast walls, orto an elevated roadway supported thereby, obviating the need forextremely precise location of the foundations.

Other objects of the invention will become apparent from the followingdescription. j

In summary, according to the invention separately cast concretestructures (for convenience sometimes referred to as the supporting andsupported structures, respectively)` have initially exposed surfacesadapted to lie in opposed and spaced relation in the completed,composite structure, and each structure has embedded therein one or moremetal reinforcing rods that project from the said exposed surfaces. Thesupported'structure is positioned in relation to the supportingstructure with the said surfaces thereof in opposed and spaced relationand brought to the precise desired relative position, eg., byorientation and leveling, and held in such position. The reinforcingrods, which are preferably located in their respective structures inYsimilar geometric patterns so as to be substantially in alignment whenthe structures have the desired relative positions, are then firmlyconnected together, preferably by welding or by clamps, so as to bondeach of the rods of the supported structure to one or more rods of thesupporting structure to insure the transmission of tensile stressbetween connected rods. The intervening Space or gap between the exposedsurfaces is then filled with a suitable load-sustaining filling materialthat includes a fresh hydraulic cementitious aggregate of thenonshrinking type which hardens to form a firm? mass (expandingcementitious aggregates being included' among non-shrinking aggregates)to enclose or embed the connected reinforcing rods and cover the exposedsurfaces and substantially parallel to one another; in the case of acolumn or wall mounted above a foundation, or a'girder supported above acolumn or wall, the rods are substantially vertical and these surfacesare horizontal; however, in some embodiments, e.g., when a beam is xedto a column, girder or wall, the surfaces may be horizontal, vertical orat some other inclination, and when two oor slabs are united thesurfaces are usually vertical. The supported structure may be held inthe desired position in relation to the supporting structure by anysuitable means such as a derrick, crane, temporary tower, scaffolding, aleveling jack that may support the structure during orientation andleveling, or the like, or a combination thereof. The connection betweenthe rods that project from the several structures is advantageously suchas to permit loading of the rods throughout their lengths to the fulltensile strengths thereof. For this reason it is preferred, when weldingis employed, to make the rods long enough to overlap throughout themajor part of the intervening space between the said exposed surfaces,and to weld the overlapping rods substantially along the full distanceof the lap, e.g., for about 6-12 inches in the case of quarter-inch rodsand proportional distance for rods of other diameters. Overlapping,though preferred, is not essential, and a separate tie member may beused to connect non-overlapping rods or to strengthen a connectionwherein an insufiicient overlap occurs.

Considering the filling material in greater detail, it is well knownthat mortars, grouts, and concrete aggregates, herein genericallyreferred to as hydraulic cementitious aggregates, when made from usualconstruction material shrink upon setting. Were such an aggregateemployed alone to fill the intervening space between the exposedsurfaces of the juxtaposed structures to be connected, the fillingmaterial would, after hardening, no longer fill the space completely andbear uniformlyV against the said surfaces; instead, only parts of thefilling material would make Contact and, in extreme cases, an actualsmall gap may result. This prevents a uniform distribution ofcompressive stresses over the cross sectional area of the surface, andmay result in progressive failure, particularly when the connection issubjected to a bending moment. Since the reinforcing rods are in suchcase either slack or actually in compression (c g., when the supportedstructure s resting on a supporting structure beneath it) they do notfunction to anchor the supported structure securely to the suportingstructure, and an undesirably large relative motion between thestructures may result from the application of a force of a givenmagnitude to the supported structure. For example, when the supportedstructure is a column resting on a foundation and a tilting forceapplied to the column, a definite tilting movement would occur in thecolumn before the rods at the side of the column from which the forceacts are sufficiently stressed to counteract the resulting bendingmoment.

Now, according to the invention, this diliiculty is overcome by usingfor at least a part of the load-sustaining filling material a specialhydraulic cementitious aggregate, 'known per se, which is non-shrinking,i.e., which at least maintains its volume during setting and hardens toform a firm mass. Such an aggregate may have the property of maintainingits volume substantially unchanged during setting, but preferably is ofthe expanding type, whereby the reinforcing rods are placed under slightor considerable tension during the setting. The welded or otherwiseconnected rods may be optionally loaded slightly in tension prior tofilling the intervening space by adjustment of the leveling device, orby other means exerting a force tending to separate the said surfaces,but this is not necessary, particularly in the latter case. It ispreferred to employ the non-shrinking cementitious aggregate only for yapart of the load-sustaining material, as by filling up the greater partof the aforementioned intervening space with solids or ordinary concrete(which may be of the shrinking type) leaving a smaller space into whichthe nonshrinking aggregate is tamped after the previously emplacedconcrete has hardened. By this preferred method the expansion of thelatter aggregate can cause only a small tensioning of the reinforcingrods, insufficient to destroy the bond of the latter to their respectivestructures or to the major part of the load-sustaining material. Thisfeature is useful in that it permits the use of aggregate that isdefinitely of the expanding type without a very precise control of theamount of expansion, because mixtures that do not either expand orcontract or those that expand to accurately specified limits are moredidicult to use in practical construction work. In certain instances, aswhere the said exposed surfaces are vertical, this preferred methodinvolves the inconvenience of placing a vertical spacer board adjoiningone of the exposed surfaces to fill part of the gap while the remaining,major part of the gap is filled with ordinary concrete and subsequentlyremoving the spacerboard and filling the resulting thin gap -withexpanding aggregate; in this case recourse may be had to an alternatemethod, wherein the entire gap is filled with an aggregate of the samecomposition, the content of the expanding cement or expanding ingredientthereof being more carefully controlled to avoid excessive expansion.

ln the resulting structure the welded rods are preferably under tensilestress while the load-sustaining material between the surfaces of thesupport and the pre-cast structure is under compressive stress. Thisload-sustaining material is a body of cohesive aggregate, i.e., hardenedcementitious aggregate, extending continuously between the saidsurfaces. In other words, the filling material is thus loaded withoutinterposing a wedge, screw or the like.

The invention will be described in greater detail with reference to theaccompanying drawings forming a part of this specification andillustrating certain preferred embodiments, wherein:

Figure 1 is an exploded elevation view showing the elements used formaking the connection;

Figure 2 is a horizontal sectional view taken on line 2-2 of Figure l;

Figure 3 is an isometric view of the completed structure;

Figures 4-7 are vertical sectional views through a foundation and lowerpart of a column showing successive stages of the method of erection;

Figure 8 is a vertical sectional View taken on line 8--8 of Figure 9showing a modied connection applied for connecting a beam to a wall;

Figure 9 is an elevation of the connection according to Figure 8;

Figure 10 is a sectional view through a further modification showing abeam connected to a vertical surface of a wall or column;

Figure 11 is an elevation view showing an alternate connection betweenreinforcing rods;

Figure 12 is a sectional view taken on line 12--12 of Figure 13 showinga further application of the invention for joining concrete floor slabsthat are cast separate from supporting columns;

Figure 13 is a sectional view taken on line 13--13 of Figure l2;

Figure 14 is a sectional view of a modified construction wherein thefloor slabs are cast integrally with the beams `and the invention isapplied for joining adjacent slabs;

Figure 15 is a sectional view showing the invention applied toconnecting a floor beam to a girder taken on line l5-15 of Figure 17;

Figure 16 is a sectional view taken on line 16--16 of Figure 15; and

Figure 17 is a fragmentary plan view, on a reduced scale, of theconstruction according to Figures 15 and 16.

The invention will 'be illustrated in Figures 1-7 by way of example asapplied to the erection of a double stanchion for supporting pipes andthe use of an internal leveling device' will be shown; however, it willbe' understood that other types of structures, as previously indicated,and other types of leveling devices, such as externally applied jacks ortowers, fall within the scope of the invention.

Referring to the drawings, Figures 1 3, 10 and 11 are concretefoundations which may be bell-bottom footings located entirely beneaththe ground level 12 having at, upper exposed, horizontal surfaces 13. Adouble stanchion 14 has a pair of columns 1S and 16, each of which has alower, exposed, horizontal terminal surface 17 The stanchion isprefabricated of concrete prior to erection and has suitable metalreinforcing rods of which only the rods 1S are shown. These rods areembedded in the concrete and project downwardly beneath the surface 17.Any suitable number, e.g., four, of such projecting rods arranged as arectangle may be used on each column.

Each footing has a corresponding number of, viz., four, verticalreinforcing rods 19 rmly embedded therein and projecting upwardly beyondthe surface 13 at locations to be substantially in alignment withcorrespoding rods 18, i.e., in juxtaposition thereto, when thecorresponding column is placed in position above the footing asindicated in Figures l and 4-7. The proper relationship of thereinforcing rods 18 and 19 can be obtained by the use of woodentemplates that position the rods prior to and during the casting of theconcrete. A plurality of shorter vertical reinforcing rods 20 areoptionally, although preferably, embedded in each footing so as toproject upwardly `above the upper ends of the rods 19 at positionsoutside of the rectangle defined by the rods 19 and laterally beyond thecolumns 15 and 16, as shown in Figure 2. A suitable leveling device may,if desired, be embedded in each footing; thus, a hollow tube 21 may beembedded at the central axis and project upwardly above the surface 13.The leveling device further includes an externally threaded tube 22adapted to'have a sliding t within the tube 21 and having an enlargedbearing plate 23 at the top. A nut 24 is threaded on to the tube 22 andis wide enough to engage the upper edge of the tube 21; it may beprovided with lugs 25 for receiving a spanner wrench.

To make the connection the stanchion 14 is erected to position thecolumns 15 and 16 over the footings 10 and 11 by means of a suitablederrick (not shown) with the surfaces 13 and 17 in opposition and invertically spaced relation so as to leave .an intervening space ofconvenient height, such as twelve inches. The subsequent operations willbe described with reference to Figures 4-7 in which only one of thefootings on `columns is shown, it being understood that both connectionsare made simultaneously and in the same manner. As shown in Figure 4,the stanchion is rst placed on the plate 23 so as to be supportedthereby, and is leveled by adjusting the nut 24 to bring the surface 17to the desired elevation; leveling of a stanchion in a directiontransverse to the vertical plane joining the two footings is alsoeffected, using an external support, not shown. When the stanchionV isproperly positioned each rod 18 is next to a corresponding rod 19; `ifnecessary, these rods are bent slightly to bring them into contact.

The contacting rods are then welded continuously as i indicated at 26.It will be noted that the reinforcing rods 20 extend above the surface17. It is advantageous to make the cross sectional area of the weldequal to that of one reinforcing bar.

Referring to Figure 5, an annular reinforcing tieV rod 27 is attached tothe welded vertical rods and a` second annular reinforcing tie rod 28 isattached to the lower portions of the rods 20. These annular reinforcingrods, although preferred, are optional. v

A form 29 is then built around the rods and concrete 30 is poured intoit to a level A slightly below the surface 17, thereby leaving a freespace which may suitably have a height of one to several inches.

Referring to Figure 6, when the concretel 30` is dryv and has completedsubstantially all of the shrinkage that accompanies setting, a hydrauliccementitious aggregate of the type that does not shrink upon setting,such as dry grout 31, is placed into the space immediately beneath thesurface 17. It is preferable to roughen the upper surface of theconcrete 30 and the surface 17 prior to introducing the grout. By drygrout is means a fresh mixture of line aggregate and hydraulic cementcontaining only enough water to permit setting but insuicient to form aplastic mix. The cement should consist of or contain ingredients thatprevent shrinkage upon setting or which, preferably, cause a slightdegree of expansion upon setting. Such ingredients are metallicaggregates having the quality of expanding in volume during the settingand curing stages, forming a void-filling staple ingredient that isinsoluble in water. They may contain iron particles or iron in theferrous form which oxidize during setting, and may include an alkali tocause oxidation. An example of such an ingredient is Embeco described inThe Action of Embeco in Concrete and Mortars, published by The MasterBuilders Company, Cleveland, Ohio, 1935. The grout should be tamped andhammered to pack it carefully and to ll all voids. The ce-v though thepreferred use of two bodies of lilling materiall 30 and 31 was describedit is evident that the expanding or non-shrinking aggregate 31 may insome instances be used to fill the entire space between the surfaces 13and 17. If desired, the welded rods can be tensioned slightly prior tolling the space between the surfaces 13 and 17, e.g., by turning the nut24 on the leveling jack. This is particularly advantageous when thegrout is of the type that does not either shrink or contract appreciablyduring setting, and may be used to form a pre-stressed connection.

Referring to Figure 7, after the concrete or grout 31 has set for aboutten hours a third annular reinforcing tie rod 32 may be attached to therods 20 near their upper ends. The form is then extended by adding asection 33 and concrete 34 is poured around the edges of the concrete 31and the lower side portions of the column 15 to form a protective shroudfor the grout. After setting, the forms are stripped resulting in astructure having the appearance indicated in Figure 3.

Any difference in color between the dry grout 31 and the surroundingconcrete areas can be remedied by applying a suitable cement wash to thesurfaces concerned after the grout is thoroughly dry; this makes theapplication of the protective shroud 34 unnecessary in many cases.

Referring to Figures 8 and 9, a reinforced concrete the lower exposedsupporting surface 45 of the beam. f

The reinforcing rods 41 project upwardly from the surface 44 to a heightslightly below that of the surface 45.

The beam 43 has a plurality, e.g., four, reinforcing rods 46 embeddedtherein and projecting vertically downwardly from the surface 45, therebeing one rod 46 opposite each rod 4l. Some of these rods may, ifdesired, be

integral with the lower longitudinal reinforcing rods 47 of the beam,while others may be inclined as shown at 46a to transmit shear, andextend hoizontally to their ends, indicated at 4Gb. They may, ifdesired, be fixed to the upper reinforcing rods 47a.

In making the connection the pre-cast beam 43 is placed into the notch42 and supported and leveled precisely,

both longitudinally and transversely, with the surfaces 44 and 45 inspaced relation to leave an intervening space; the leveling device inthis case may be an external jack, indicated diganimatically at 48. Eachrod 4l is then welded to a corresponding rod 46, as indicated at 49, anda layer of concrete 50 is cast to fill the major part of the interveningspace. When this concrete has set and completed its shrinkage, the upperand lower surfaces of the remaining space are roughened and a layer ofnon-shrinking aggregate, such as dry grout l,- which is preferably ofthe expanding type, is t-amped into this space and permitted to set toform a firm mass. It is evident that suitable forms, as previouslydescribed, as well as reinforcing rods may be used for the concrete 50and aggregate 51. In this case, however, a cement wash would bepreferred to the concrete shroud. The space between sides of the beam 43within the notch 42 may be grouted, using grout similar to the grout 51or ordinary grout.

Referring to Figure l0, there is shown a connection to a wall 66 thatprovides a vertical surface 6l., and may extend above the top of thehorizontal vbearn 62 to be supported thereby. This embodimentillustrates the application of the invention to the case wherein theexposed surfaces are vertical and the connected reinforcing bars arehorizontal.

The wall 66 has embedded therein horizontally projecting metal rods 63which are firmly bonded to the wall, e.g., welded to the upright metalreinforcing rods 64 of the wall and/ or provided with large heads 65;the rods 63 may be made integral with the upright rods 64 and curved inthe manner previously described for the bars 46 and 47 in Figure 8. Theprojecting rods 63 are arranged in a geometric pattern similar to thatof the longitudinal reinforcing rods 66 of the beam, the latter rodsprojecting horizontally beyond the vertical, initially exposed terminalsurface 67 of the beam; thus, four rods '63 and four rods 66, situatedat the corners of a rectangle, may be used. The wall further has ashoulder or haunch 68 cast integrally therewith and provided with metalreinforcing rods 69 and 70. The beam 62 may have reinforcing rods 71with inclined portions, as shown, to improve transmission of shear.

In making the connection the beam may be supported in various Ways:according to one method it is supported and leveled precisely by meansof a jack 4S, independently of the haunch 68, leaving a small gapbetween the latter and the beam. The surfaces 61 and 67 of the wall andbeam are thereby placed in opposed and horizontally spaced relation.Each horizontally projecting rod 63 is then welded to a correspondinghorizontally projecting rod 66, as indicated at 72. The interveningspace between the surfaces 6l and 67 `and the space between the haunchand the bottom of the beam are then lled with fresh dry grout 73 of thenon-shrinking type and, preferably, of the expanding type, which hardensinto a rm mass, the grout being well tamped into position and retainedby suitable forms, not shown. The grout, when of the expanding type,mayv cause a rise in the height of the beam but this is negligibly smallbecause the layer of grout beneath the beam is quite thin. Expansion ofthe grout places the rods 63 and 66 under tension. Since the entirespace between the surfaces 61 and 67 is, in this embodiment, filled withgrouut of the same composition, it is desirable to control the amount ofthe expanding ingredient of the grout to avoid excessive expansion suchas would tension the rods sufficiently to destroy their bonds to thewall and beam.

According to another method, the beam 6'2 may be placed directly on thehaunch 68 without the leveling jack; the other operations are asdescribed above, except that no grout is placed beneath the beam. Withthis method it is not possible to adjust the exact height of the beamindependently of the haunch.

As was stated above, the projecting rods of the several juxtaposedstructures may be connected by means other than welding. An alternativemeans suitable 'for use in areas wherein welding is not permissible, isdisclosed in Figure l1, showing separately cast structures 75 and 76,having projecting reinforcing rods 77 and 78, respectively. When thesestructures are placed in the desired relative positions, the rods aresecured by means of clamps 79 and 80, each comprisinga U-bolt S1, a wirerope clip 82 and a pair of nuts, of which only the nut rS3 is visible inthe drawing. The invention may also be applied to connecting separatelycast concrete slabs which may or may not have integral supporting beams.

Referring to Figures 12 and 13, which show the application of theinvention to the joining of floor slabs that are separate from theirsupporting beams 43 that may be disposed in parallel relation `andsupported in any manner, eg., in notches in walls such as the Wall 49 aspreviously described for Figures 8 and 9, by welding the terminal,vertical parts of the horizontal reinforcing rods 47 and 47a of thebeams at 49' .to vertical rods of the wall and filling the interval withconcrete 50 and expanding grout 5l. In addition to the horizontalreinforcing rods 47 and 47a the beams have embedded therein uprightstirrups 84 that extend above the beams at the center line and havetheir upper, horizontal traverses spaced above the beam by 'a distanceless than the thickness of the floor slab to be supported. The floorslabs 85, 85a and 85h, are cast separately from the beams and wall andhave widths great enough to span the interval between adjacent beams 43but less than the center-to-center distance between such beams, so as toleave horizontal intervals between the vertical marginal surfaces ofeach pair of juxtaposed slabs resting on the same beam. The floor slabscarry suitable horizontal metal reinforcing rods S6 at a suitable level,eg., about a third of thi-ckness above the bottom. Reinforcement mayalso be provided at a higher level as indicated at 87 by providingadditional reinforcing rods or by` bending some of the rods 86 up nearthe lateral margins. At least some of these rods project horizontallybeyond the marginal surfaces of the slabs for distances suflicient toprovide overlap between opposed rods on the juxtaposed slabs.

In assembling Ithe slabs, the latter are first placed on the beams 43with the margins in supporting engagement thereon and the stirrups 84are connected to the reinforcing rods 86, preferably by welding. lTheopposed reinforcing rods l86 and 87 of the juxtaposed slabs are thenconnected, eg., by welding as indicated at 8S. Dry grout of thenon-shrinking type, preferably the expanding type, is then tamped intothe interval between the slabs as shown at 89 and allowed to set toform4 a firm mass thereby effectively loading the bars 86 and 37. Thecompleted connection is able to transmit bending moment, i.e., the upperrods 87 are loaded in tension and the lower part of the grout 89 isloaded in compression;

1 for this reason the connection between the lower reinforcing rods 86could be omitted under certain design loading conditions. At the centerof the span between beams the slabs are, of course, subjected to abending moment inthe opposite sense, and inflection points occur betweenthe 'center and the margins of the slab. It 'may be stated, however,that the invention is not strictly limited to cases wherein thereinforcing rods 86 and 87 are provided at different levels; in Vsome`floor slabs, rods are provided only at one level, sometimes near themid-level, and the connection according to the invention is alsoapplicable to joining such slabs.

Referring to Figure 14, showing the invention applied to the joining ofseparate floor slabs that are cast integral to the beams, the floorslabs 90 project laterally to both sides of their beam portions 91, thelatter being supported in any manner, eg., Vin the wall 40 as describedabove for the beams 43. The combined beams and 'licor slabs carrysuitable longitudinal reinforcing bars, of which only the rods 92 areshown, and Vtransverse reinforcing bars 93 that are preferably below themid-level of the slab and may extend downwardly into the beam portionsand anchored therein, as shown. The structures may be further reinforcedwith reinforcing bars 94 at a higher level above the beam portions fortransmitting shear and to strengthen the structure for cantileverloading. The bars 93 project beyond the vertical marginal surfaces 95 ofthe slabs and the beam portions are mounted in spaced relation so thatthe vertical surfaces 95 of juxtaposed slabs are spaced apart, with thebars 93 of the respective slabs overlapping.

For connecting the floor slabs the projecting opposed bars 93 of thejuxtaposed slabs are first firmly connected, e.g., by welding as shownat 96. The gap between the surfaces 95 is then filled withnon-shrinking, preferably expanding, grout as indicated at 97, asuitable form (not shown) being provided. When the grout hardens to forma firm mass the interval between the surfaces 95 is filled completelyand, when expanding grout is used, the rods 93 may be loaded slightly intension. The conjoined slabs are thereby adapted to be subjected to abending moment such that the upper part of the slab is in compression.

Referring to Figures 15-17, a reinforced concrete girder 100 is used tosupport the intermediate parts of a series of parallel, separately cast,reinforced concrete beams 101, 102, it being understood that the beamsare additionally supported by walls or by other girders, not shown,extending parallel to the girder 100. The girder 100 may be supported inany suitable manner on columns or the like, e.g., on haunches 103projecting from a wall 104. Separately pre-cast `reinforced concretefloor slabs 10S, 107, extend between adjacent beams or between the wall104 and a floor beam The beams have central tongues or ridges 101a,102a, extending the full lengths of the beams and shoulders 101b, 102b,on both sides of the ridges for supporting the slabs. Similarly, thewall 104 has a tongue or ridge 104e: at the outer side thereof, leavinga supporting shoulder 104b. The slabs rest on these shoulders and arepositioned by the ridges; they have suitable metal reinforcing rods 108,109, extending across the span and parallel to the beams, respectively.The point of novelty in this construction resides in the connectionbetween the girder and beams.

The girder 100 has the upper part thereof notched as indicated at 110,Figure 15, at each crossing of a beam while each beam 101, 102, etc.,has the lower par-t thereof notched as indicated at 111, Figure 16, ateach girder. Vertical thrust is thus transmitted through the plane ofcontact 112 between the bases of the notches. As seen in Figure 15, thenotches 110 need not be made subs-tantially longer (along the length ofthe girder) than the width of the beam, and they are usually made onlylarge enough to permit the beams to be inserted without binding intoaligned notches on a number of girders. The notches 111 on the beamsare, however, longer (along the length of the beam) than the width ofthe girder. The depths of these notches are such that the shoulder 10117of each beam is at about the level of the top ofv the girder. The girdercarries suitable metal reinforcing rods, such as longitudinal rods 113and 114. Beneath each notch the girder has transverse metal reinforcingrods 115 embedded therein and projecting laterally beyond both sides ofthe girder, the overall lengths of the rods 115 being slightly lessthan.- the total width of the notches 111 in the beams. These rods 115may be fixed, e.g., welded, to the rods 113.. `The beams carrylongitudinal'reinforcing rods 116 and 117, the latter being at the levelof the notches 111 and almost in alignment with the rods 115 so as to bein touching, side-'byside relation. As shown in Figure 16, the rods 117project into the notch 111 so as to overlap lthe rods 115. Some of therods` 117 may be bent up over thel notch,

10 as indicated at '117m The rods 116 and 117 may be connected by loopedrods 118.

In assembling the structure, the girders are first emplaced and thebeams-101, 102, `are tted with the notches in interlocking relation andthe projecting rods in overlapping relation to the projectingrods 117.

' The overlapping rods are then firmly connected, eg., by

welding as shown at v1119. Dry grout of the nonshrinking or, preferably,`of the expanding type is then tamped into the space between the beamand girder surrounding the connected rods to fill the notch 111 andallowed to set to form a firm mass. A suitable form, not shown, may beprovided for this operation. The notch 110 may be similarly filled withgrout. The floor slabs 105-107 are then placed on the beams and-wall,secured by any conventional or suitable means, such as hold-down bolts(not shown), and the spaces between the slabs and the ridges are lledwith grout, as indicated at 121. The slabs may, of course, be attachedby the arrangement shown in Figures 12 and 13, in which case the beamswould have at upper surfaces. The grout |'120, when hardened,effectively loads the lower portions of the beams in compression,thereby better adapting the beams for sustaining loads that subject itto bending moments at the girders in which the lower parts of the beamsare loaded in compression.

I claim as my invention:

l. Method of making a connection betweenl two separately cast concretestructures each of which has ernbedded therein metal reinforcing rodsprojecting outwardly from a surface thereof, comprising the steps of:positioning the said pre-cast structures with the said surfaces thereofin opposite and spaced relation so as to leave a free intervening space;firmly securing each rod projecting from one of the structures to a rodprojecting from the other structure to form for each rod a connectionadapted to transmit tensile stress; thereafter maintaining the intervalbetween said surfaces so as to hold the connected rods tautly and llingthe said intervening space completely between the said surfaces with aload-sustaining material that consists essentially of a hydrauliccementitious aggregate of the type that contains expanding cement inamount at least to maintain its volume against shrinking during settingand hardens to form a firm, essentially non-plastic mass; and allowingthe said hydraulic cementitious aggregate to set, whereby the portionsof said connected rods between said surfaces are secured tautly aftersetting.

2. Method according to claim 1 wherein said surfaces are positioned toeffect an overlap between the oppositely projecting rods over the majorpart of the distance between said surfaces and the rods are secured bywelding along substantially the full length of the overlap.

3. Method according to claim 1 wherein the step of lling the interveningspace includes the following oper-- ations: lling the major part of saidspace with concrete that hardens to form a firm, essentially non-plasticmass and leaving a small clearance immediately adjacent one of saidsurfaces; allowing said concrete to set; and thereafter tamping a drygrout into said small clearance, said dry grout consisting essentiallyof the hydraulic cementitious aggregate defined in the said claim.

4. In combination with the steps of the method according to claim 3, thestep of placing a concrete shroud about the grout. Y

5. In combination with the steps of the method according to claim 1, thestep of moving said pre-cast structures slightly apart after securingthe rods and prior to lling the intervening space with theload-sustaining material to apply tension to the connected rods, andmaintaining said tension until after the said hydraulic cementitiousaggregate has set.

6. Method of making a connection between two separately cast concretestructures each of which has embedded therein metal reinforcing rodsprojecting outwardly from a surface thereof, comprising the steps of:positioning the said pre-cast structures with the said surfaces thereofin opposite and spaced relation so as to leave a free intervening space;firmly securing each rod projecting from one of the structures to a rodprojecting from the other structure to form for each rod a connectionadapted to transmit tensile stress; and thereafter filling the saidintervening space completely between the said surfaces with aload-sustaining material that includes a hydraulic cementitiousaggregate of the type that expands during setting and thereby applies atension to the connected rods and maintains said tension after setting.

7. Method of erecting a pre-cast concrete structure on a concretesupport, said structure having embedded therein metal reinforcing rodsprojecting from a surface thereof and the support having embeddedtherein metal reinforcing rods projecting lbeyond an opposed supportingsurface thereof, comprising the steps of: positioning the pre-caststructure in relation to the support with the said surfaces thereof inopposite and spaced relation so as to leave a free intervening space;firmly securing each rod projecting from the structure to a rodprojecting from the support to form for each rod a connection adapted totransmit tensile stress; thereafter maintaining the interval betweensaid surfaces so as to hold the connected rods tautly and filling thesaid intervening space completely between the said surfaces with aload-sustaining material that includes a hydraulic cementitiousaggregate of the type that contains expanding cement in amountat leastto maintain its volume against shrinkage during setting and hardens toform a firm, essentially nonplastic mass; and allowing the saidhydraulic cementitious aggregate to set, whereby the portions of saidconnected rods between said surfaces are secured tautly after setting.

8. Method of erecting a pre-cast concrete structure on a concretesupporting base, said structure having embedded therein metalreinforcing rods projecting downwardly beneath a downwardly directedsurface thereof and the base having embedded therein metal reinforcingrods projecting upwardly beyond an upwardly directed supporting surfacethereof, comprising the steps of: positioning the pre-cast structureabove the base with the said surfaces thereof in opposite and verticallyspaced relation so as to leave a free intervening space; lrrnly securingeach rod projecting kfrom the structure to Va rod projecting from thebase to form Vfor each :rod a connection adapted to transmit tensilestress; and thereafter iilling the said intervening space completelybetween the said surfaces with fa load-sustaining'material that includesa hydraulic cementitious aggregate of the type that expands duringsetting and thereby applies va tension to the connected rods andmaintains said tension after setting.

9. Method of connecting a horizontal pre-cast concrete beam having asubstantially vertical surface to an upright concrete support having asubstantially vertical surface, said beam having embedded therein metalrods projecting horizontally beyond said surface thereof and saidsupport having embedded therein metal reinforcing rods projectinghorizontally beyond said substantially vertical surface thereof,comprising the steps of: positioning the beam in relation to the supportwtih the said surfaces thereof in opposite and horizontally spacedrelation so as to leave a free intervening space; firmly securing eachrod projecting from the beam .to a rod projecting from the support toform for each rod a connection adapted to transmit tensile stress; andthereafter filling the said intervening space completely between thesaid surfaces with a load-sustaining material that includes a hydrauliccementitious aggregate of the type that expands during setting andhardens to form a firm, essentially non-plastic mass and Ytherebyapplies a tension to the connected rods and maintains said tension.after setting.

l0. Method of connecting in `juxtaposition separately cast concretefloor slabs that have embedded therein metal reinforcing rods projectinghorizontally beyond the adjacent marginal surfaces of the slabs,comprising the steps of: positioning said iloor slabs in relation to oneanother to place said marginal surfaces in opposed and horizontallyspaced relation so as to leave a free intervening space; rmly securingeach rod projecting from one of the floor slabs to a rod projecting fromthe other floor slab to form for each rod a connection adapted totransmit tensile stress; thereafter maintaining the interval betweensaid surfaces so as to hold the connected rods tautly and filling thesaid intervening space between the said surfaces with a load-sustainingmaterial that includes a hydraulic cementitious aggregate of the typethat contains expanding cement in amount at least to maintain its volumeagainst shrinkage during setting and hardens to form a hard, essentiallynon-plastic mass; and allowing the said hydraulic cementitious aggregateto set, whereby the portions of said connected rods between saidmarginal surfaces are secured tautly after setting.

l-l. Method of connecting a pre-cast concrete beam to a separately castsupporting girder member extending transversely thereto at theintermediate parts of said members, at least one of said members havinga notch that is materially longer than the width of the other member,said one member having reinforcing rods embedded therein and projectinglongitudinally into said notch from opposite ends thereof and said othermember having a transverse reinforcing rod projecting laterally from thesides thereof, comprising the steps of: positioning said beam member onand transversely to said girder member for support thereby with saidother member at least partly within the said notch in the one member soas to leave an intervening space within the notch on each side of thesaid other member; rmly connecting each longitudinally projecting rod toa laterally projecting rod to form for each rod a connection adapted totransmit tensile stress; maintaining the intervals between the sides ofsaid other member and the ends of the notch so as to hold the connectedrods tautly and filling the said intervening spaces about the connectedrods completely between the end of the notch and the side of said othermember with a load-sustaining material that includes a hydrauliccementitious aggregate of the type that contains expanding cement inamount at least to maintain its volume against shrinkage during settingand hardens to form a rm, essentially non-plastic mass; and allowing thesaid hydraulic cementitious aggregate to set, whereby the portions ofsaid connected rods within said loadsustaining material are securedtautly after setting.

l2. Method of connecting a pre-cast concrete beam to a separately castsupporting girder at the intermediate parts of the beam and girder, saidgirder having an upwardly open notch of a length at least equal to thewidth of the beam and the beam having a downwardly open notch of alength materially in excess of the width of the girder, said beam havinga longitudinal reinforcing rod embedded therein and projectinglongitudinally into the latter notch from at least one end thereof andsaid girder having a transverse reinforcing rod projecting beyond a sideof the girder beneath the said notch therein, comprising the steps of:positioning said beam on the girder transversely thereto with the saidnotches in interlocking relation for support of the beam between basesof the notches with the said reinforcing rods in juxtaposition so as toleave an intervening space within said notch of the beam on each side ofthe girder whereat a reinforcing rod projects; welding eachlongitudinally projecting rod of the beam to a laterally projecting rodof the girder; and thereafter filling the said intervening spacecompletely between the end of the notch and the side of the girder with-a load-sustaining material that includes a hydraulic cementitiousaggregate of the type that expands during setting and hardens to fonn ahrm, essentially nonplastic means and thereby applies a tension to theconnected rods and maintains said tension after setting.

13. IThe combination uniting separately cast, metalrcinforced concretestructures which comprises: a first and a second pre-cast concretestructure, each said structure having a bounding surface and the saidbounding surfaces of the structures being situated in opposed and spacedrelation, each of said structures having a plurality of metalreinforcing rods embedded therein and projecting beyond said surfacethereof towards the other structure; a irm connection between each ofthe said reinforcing rods projecting from one structure and areinforcing rod projecting from the other structure adapted to transmittensile stress; and a rm, essentially non-plastic and cohesive,load-sustaining material consisting essentially of hardened hydrauliccementitious aggregate which contains hardened expanding cementextending continuously between said surfaces and surrounding the saidprojecting rods and the said connections thereon, said material beingunder compressive stress and said connected projecting reinforcing rodsbeing under tensile stress.

14. A combination according to claim 13 wherein said precast concretestructures are concrete oor slabs, said terminal surfaces thereof areadjacent lateral marginal surfaces thereof, and said reinforcing rodsproject horizontally from said marginal surfaces.

15. In combination with the elements recited in claim 14, a support beamhaving an upwardly projecting metal reinforcing rod embedded therein,the said lateral margins of the two oor slabs being in supportedengagement on the said beam on opposite sides of said upwardlyprojecting rod, the last-mentioned rod being rmly secured to saidhorizontally projecting rods of the floor slabs, and the said rods ofthe *door slabs and the said load-sustaining material being all situatedabove the said support beam.

16. In combination with the elements recited in claim 14, a pair ofspaced support beams, each said oor slab being supported at theintermediate part on one of the said beams and projecting laterallybeyond said beams, the said adjacent marginal surfaces of the floorslabs are situated between the said support beams.

17. A combination according to claim 13 wherein one of said concretestructures is a girder member and the other is a beam member extendingtransversely thereto, at least one of said members having a notch thatis materially longer than the width of the other member and said othermember being situated at least partially within the notch with the sidesthereof in spaced relation to the ends of the notch, each end of saidnotch constituting a bounding surface of the member containing the notchand each side of said other member constituting a bounding surfacethereof.

18. The combination uniting a pre-cast concrete girder and a separatelypre-cast concrete beam which comprises: a girder having an upwardly opennotch at an intermediate part thereof, said notch having a length atleast equal to the width of the beam; a beam extending transversely tothe girder having a downwardly open notch at an intermediate partthereof and supported from said beam through the bases of the saidnotches, said notch in the beam having a length which is materially inexcess of the width of the girder and extends to each side of thegirder; a longitudinal metal reinforcing rod embedded in the beam oneach end of the notch and projecting longitudinally into said notchtoward the girder; a transverse metal reinforcing rod embedded in thegirder beneath the notch therein and projecting laterally beyond thesides of the girder into the notch in the beam; a iirm connectionbetween each said longitudinally projecting rod and said transversemetal rod; and a rm, essentially non-plastic and cohesive,load-sustaining material consisting essentially of hardened hydrauliccementitious aggregate which contains hardened expanding cementlextending continuously between each side of the girder and the ends ofthe notch in the beam and surrounding the said projecting rods and thesaid connections thereon, said material being under compressive stress.

19. The combination uniting a concrete base and a structure comprising:a pre-cast concrete base having an upwardly directed supporting surfaceand a plurality of metal reinforcing rods embedded therein andprojecting upwardly above said surface; a pre-cast concrete structuresupported by said base and having a downwardly directed surface situatedin vertically spaced relation above said supporting surface, saidpre-cast structure having metal reinforcing rods embedded therein andprojecting downwardly below said surface thereof; a rm connectionbetween each said reinforcing rod projecting from the structure to acorresponding reinforcing rod projecting from the base adapted totransmit tensile stress between the rods; and a iirm, essentiallynon-plastic and cohesive, load-sustaining material consistingessentially of hardened hydraulic cementitious aggregate which containshardened expanding cement extending continuously between said surfacesand surrounding `the said projecting rods and the said connectionsthereon, said material being under compressive stress and said weldedrods being under tensile stress.

20. A combination according to claim 19 wherein said downwardlyprojecting rods are arranged in a pattern corresponding to the patternof the upwardly projecting rods and each rod is substantially inalignment with the downwardly projecting rod connected thereto, bothgroups of rods extending sufliciently beyond their respective surfacesto overlap over a major part of the vertical distance between the saidsurfaces, and said firm connections are weldments extendingsubstantially over the full lengths of the overlapping portions of therods.

References Cited in the tile of this patent UNITED STATES PATENTS2,053,562 Jorgensen Sept. 8, 1936 2.483,175 Billner Sept. 27, 19492,580,174 Henderson Dec. 25, 1951 FOREIGN PATENTS 376,308 Great BritainJuly 8, 1932 451,798 Italy Sept. 26, 1949 591,431 Great Britain Aug. 18,1947 665,855- Great Britain Jan. 30, 1952

